package com.lagou.sqlSession;

import com.lagou.pojo.Configuration;
import com.lagou.pojo.MapStatement;

import java.beans.IntrospectionException;
import java.lang.reflect.*;
import java.sql.SQLException;
import java.util.List;

/**
 * @author jsy
 * @description: TODO
 * @date 2021/8/28 20:03
 */
public class DefaultSqlSession implements SqlSession {

    private Configuration configuration;

    public DefaultSqlSession(Configuration configuration) {
        this.configuration = configuration;
    }

    @Override
    public <T> List<T> selectList(String statementId, Object... params) throws SQLException, IllegalAccessException, IntrospectionException, InstantiationException, NoSuchFieldException, InvocationTargetException, ClassNotFoundException {
        //调用simpleExecutor
        SimpleExecutor executor = new SimpleExecutor();
        MapStatement mapStatement = configuration.getStatementMap().get(statementId);
        List<Object> query = executor.query(configuration, mapStatement, params);
        return (List<T>) query;
    }

    @Override
    public <T> T selectOne(String statementId, Object... params) throws SQLException, IllegalAccessException, IntrospectionException, InstantiationException, ClassNotFoundException, InvocationTargetException, NoSuchFieldException {
        List<Object> objects = selectList(statementId, params);
        if(objects.size()<1){
            throw new RuntimeException("查无数据");
        }else if(objects.size() == 1) {
            return (T) objects.get(0);
        }else {
            throw new RuntimeException("查询结果过多，请检查数据");
        }
    }

    @Override
    public int executeQuery(String statementId, Object... params) throws SQLException, IllegalAccessException, IntrospectionException, InstantiationException, ClassNotFoundException, InvocationTargetException, NoSuchFieldException {
        //调用simpleExecutor
        SimpleExecutor executor = new SimpleExecutor();
        MapStatement mapStatement = configuration.getStatementMap().get(statementId);
        int result = executor.executeQuery(configuration, mapStatement, params);
        return result;
    }
    @Override
    public <T> T getMapper(Class<?> mapperClass) {
        // 使用JDK动态代理来为Dao接口生成代理对象，并返回

        Object proxyInstance = Proxy.newProxyInstance(DefaultSqlSession.class.getClassLoader(), new Class[]{mapperClass}, new InvocationHandler() {
            @Override
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                // 底层都还是去执行JDBC代码 //根据不同情况，来调用selctList或者selectOne
                // 准备参数 1：statmentid :sql语句的唯一标识：namespace.id= 接口全限定名.方法名
                // 方法名：findAll
                String methodName = method.getName();
                String className = method.getDeclaringClass().getName();
                String statementId = className+"."+methodName;
                if("insert".equals(methodName) || "delete".equals(methodName) || "update".equals(methodName) ){
                    int result = executeQuery(statementId, args);
                    return result;
                }
                    // 准备参数2：params:args
                    // 获取被调用方法的返回值类型
                    Type genericReturnType = method.getGenericReturnType();
                    // 判断是否进行了 泛型类型参数化
                    if(genericReturnType instanceof ParameterizedType){
                        List<Object> objects = selectList(statementId, args);
                        return objects;
                    }
                    return selectOne(statementId,args);
                }
        });

        return (T) proxyInstance;
    }
}
